208 Memoir of Rev. John Prince, LL. D. 
brother who worked with him, was very sick of a fever, and requir- 
ed all his attention. The brother died. In two days more he too 
the fever himself, and died in ten days, and left me destitute of 
workmen to finish the matters | had undertaken. I got the instru- 
ment from his shop as soon as I could in the unfinished state, and 
went to work myself to complete it ; and when I had done it to my 
own satisfaction, as I supposed, to my great disappointment and 
mortification, 1 fone all the labor was lost. For, on putting the 
needle into the box, which is of a parallelogram form, about six 
tenths of an inch in width, I found the box, though made of brass, 
attracted the needle to its side and would not allow it to play freely. 
This was a circumstance entirely new and unexpected. J never 
had an idea of any kind of brass being magnetic, and could not ac- 
count for the phenomenon for some time. But on trying several - 
other pieces I found that the box was not the only one that attracted 
the needle. Several pieces did the same; others did not. This 
quality must be owing to the impurity of the brass. Some steel 
filings or small particles of iron must have accidentally mixed with 
it in casting. It would have been fortunate for me if 1 had made 
the discovery before it was worked ; but the thought never occurred 
tome. ‘Too much of our Liviedovled (considering the shortness of 
life) comes to us by dear bought experience.” 
The foregoing extract may serve to give some idea of the great 
inconveniences to which Dr. Prince was put, asa philosophical me- 
chanician, from the want of workmen, and from the necessity of 
accumulating for himself his own ‘“ dear bought experience,” with- 
out. Mitsining any benefit from the experience of others. 
In looking through these manuscript volumes, we perceive, from 
the beginning to the end, the evidences of his wisdom, ingenuity, 
and skill. In one of his letters (Sept. 24, 1795,) he recommends @ 
new construction of thermometers, in which zero should be at the 
freezing point of mercury, thereby avoiding the inconvenience of 
having both plus and minus in the scale. 
In another letter (Dec. 4, 1795,) he describes some improvements 
he had introduced in the construction of an equatorial. 
Feb. 13, 1797, he gives an account of a magic lantern, contri- 
ved and constructed by him on a new and extensive scale. 
He thus introduces the description of another of his inventions, 
in a letter to William and Samuel Jones, of London, Oct. 20, 
1797—* I have lately constructed a very large microscope for my- 
